The present invention relates to a cathode for a flat panel display device, and particularly to a thermionic emissive line cathode for such a display device.
There has been developed a cathodoluminescent flat panel display which includes an evacuated envelope having substantially flat front and back walls secured together in spaced, substantially parallel relation by side walls. A plurality of spaced, parallel support walls extend between the front and back walls and divide the envelope into a plurality of channels which extend along the front and back walls between a pair of opposed side walls. In each of the channels is at least one electron beam focusing guide which is adapted to guide a beam of electrons along the channel and yet allow the beam to be deflected toward the front wall at selected points along the channel. By the expression "guiding" the beam along the channel, it is meant that the focusing guide confines the electrons in a beam as the beam travels along the channel. On the front wall of the envelope is a phosphor screen which is impinged upon when the beam of electrons is deflected out of its guide. Along one end of the channels is a gun section which contains an electron gun structure. The gun structure generates electrons and directs the electrons as beams into the beam guides.
Various gun structures have been proposed for generating electrons and directing the electrons as beams along a plurality of parallel paths. Gun structures which include thermionic emissive line cathodes are shown in U.S. Pat. No. 2,858,464 to W. L. Roberts, issued Oct. 28, 1958, entitled "Cathode Ray Tube" and U.S. Pat. No. 3,531,681 to J. T. Harden, Jr., issued Sept. 29, 1970, entitled "Flat Display Tube and Method." However, in a large size flat panel display, i.e., a display which is about 100 cm by 75 cm, there are a number of problems in using such a line cathode.